Its purpose is for manipulating chess games written in the Portable
Game Notation (PGN).
There are several ways to specify the criteria on which to extract:
textual move sequences, the position reached after a sequence
of moves, information in the tag fields, and material balance in
the ending.
Extracted games may be written out either including or
excluding comments, NAGs, and variations. Games may be given ECO
classifications derived from the accompanying file eco.pgn, or a
customised version provided by the user.